Creating an 8x8x8 3D LED Cube: It's All About the Jigs

Creating an 8x8x8 3D tricolor LED cube from the ground up involves a variety of tasks; creating custom jigs can make things much easier.

Just in case you haven't been following my columns here on EE Times -- augmented by videos on YouTube -- I'm building a 3D 8x8x8 RGB LED cube, which was inspired by this article written by our very own Max Maxfield.

Previously, I discussed the testing of 1,000 RGB LEDs and the straightening of my tinned copper wire. In this column, I will cover how I actually set about constructing the 8x8 panels for my cube. This will include more detail on the jigs I created to help me with this task. But before we start, first take a look at this video.

Cube criteria
Let's quickly establish the main criteria for my cube, so you can see where I'm coming from.

The LEDs will be of the 5mm RGB common anode variety.

The LEDs will be pitched one inch apart in the X, Y, Z planes.

The LEDs will be interconnected using 20swg tinned copper wire.

Either the wire or the LED leads will be formed into loops to provide more robust solder joints.

The construction will be as square and as straight as possible.

The cube will be made using eight 8x8 panels mounted vertically.

The eight panels will be soldered to a base PCB. (The image below shows two panels temporarily mounted on a prototype PCB.)

The front of the cube will be the flat face of an 8x8 panel with the horizontal anode rails facing forward.

The cube will be mounted centrally on the base PCB.

The PCB base will secure the cube and provide connection to other PCBs.

The top surface of the PCB will be clear of any solder joints other than the cube tails passing through it.

Any other connections to the PCB will be via surface mounted connectors on the underside.

Any control circuitry will be on separate PCBs.

The reasoning behind my choices
I decided to use 5mm LEDs because 12mm LEDs look out of proportion on a one-inch pitch. Smaller LEDs would have looked OK, but I favor the 5mm variety. I think the one-inch pitch keeps the overall construction in proportion with the 5mm LEDs. Also, the final result will be quite sturdy. A larger pitch would make the cube more flimsy, and a smaller pitch would make it look too cluttered.

My choice to use 20swg wire (instead of the 22swg I've seen used by others) was for better rigidity due to the additional wire diameter. Since the wire is twisted to improve its straightness (as discussed in my most recent column), its diameter is reduced slightly anyway. Working with straight wire eases construction and improves the cube's overall aesthetics.

The LEDs' leads will be formed into loops, and the copper wire will pass through those loops before soldering. Wire-to-wire joints will be similar. This should improve connection reliability with the drawback that replacing any LEDs that fail will be harder. I will reduce the risk of LED failures by testing them regularly throughout the construction process. Also, before the final cube assembly, I will carry out a burn-in test on all the LEDs at the 8x8 panel stage. I think 24 hours per panel should be enough to highlight any weak components.

I have no desire to solder hundreds of interconnecting wires from the cube tails to the control circuits, as I have seen others do. I know that this is, in effect, a prototype, but I really want to build this cube only once. I have the utmost confidence that it will work fine, so I will build it as if it were the final item. With this in mind, the cube will be mounted directly on a printed circuit board (PCB). Also, I want that board's upper surface -- the part visible to the observer -- to be clear of any solder joints other than the cube tails passing through it. The only other holes will be a few vias. All other connections and fixings will be on the PCB's underside.

I have considered surface mounting the control circuit components on the the main board's underside. However, I have decided to develop the control circuits on separate PCBs, thereby allowing me to modify the circuit design if I have a change of heart. This way, I won't have to remanufacture my cube, and the whole system will become much more modular.

The base PCB will have a white solder mask and black silk screen. Also, it will be manufactured professionally to present the best possible appearance -- an appearance I would never be able to achieve myself. But this comes at a significant cost. (The board design will be discussed further in a future column.)

@Max: One ay round this is to record the video with you waffling along as you go -- ignore any hesitations -- this audio is just for timing. Donl; actually video yourself speaking -- your voice is just a "voice over")

Then play the video back and re-record the sound sentence by sentence -- making multiple takes as required - edit it using a program like Audacity -- then add he sound back in -- again sentence by sentence. Just a thought...

Also, it DOES NOT have to be perfect -- the value is in the video itself -- most people will be saying "I wish I had the bottle to do that, but I hate my voice..." LOL

That's sound advice (no pun intended) and I'll give it some consideration for the next video.

@Steve: I did try and was so discusted with not the sound of my own voice per-say but more towards my presentation and the apauling hesitations.

One ay round this is to record the video with you waffling along as you go -- ignore any hesitations -- this audio is just for timing. Donl; actually video yourself speaking -- your voice is just a "voice over")

Then play the video back and re-record the sound sentence by sentence -- making multiple takes as required - edit it using a program like Audacity -- then add he sound back in -- again sentence by sentence. Just a thought...

Also, it DOES NOT have to be perfect -- the value is in the video itself -- most people will be saying "I wish I had the bottle to do that, but I hate my voice..." LOL

@Max: Why not make a short test of something with and without you speaking, then share it with me and I'll give you my honest opinion...

I really appreciate the offer and I agree with you, my latest video for panel testing truley does warrant a voice over. I did try and was so discusted with not the sound of my own voice per-say but more towards my presentation and the apauling hesitations. I just don't have the same level of confidence when speaking to another person. I think I nead some coaching and practice. If I could do it, it would save having to write all those captions, I hate writing those. On the plus side, the deaf amongst us do benefit LOL.

@Clarke: But I'm happy to see that I now have a wonderfully detailed resource to refer too, which makes the whole project that much more tempting!

I would have remained content with my 4x4x4 cube ... until I saw Steve's 8x8x8 cube developing ... now I want an 8x8x8 cube. I've already purchased the LEDs -- they are sitting in a box in my office -- but I'm forcing myself to finish some of my other projects first. Also, I want to wait till Steve finishes his because the construction details he's providing are invaluable -- I personally think this is the best such guide on the web (and I've seen a few).

@Steve: At least you have the bottle provide an audio commentary, which is something; the thought of doing fills me with dread. I did try it once and hated the result so deleted it immediately.

I think adding a spoken soundtrack does improve these instructional type videos -- it helps the audience form a connection with the presenter.

On the other hand, I know what you mean about hating the result -- I hate to hear a recording of myself speaking .... and on the other hand, I've talked to you on the phone and I think you would sound great on a video...

Why not make a short test of something with and without you speaking, then share it with me and I'll give you my honest opinion...

Terrific, I'm looking forward to watching and reading about it! And yes I will most definitely let you know when I get around to tackling my own LED cube. In fact, at that point, the trick will probably be in getting me to shutup about it.

Hi Clarke, thanks for the amazing feedback, I find your comments very uplifting and makes me feel that all the effort is worth it.

It's taking me a lot longer to build the cube than I expected mainly due to all the blogging and videos I've created. Having documented this as I go has made me stop and think things through a lot more than I would normally.

I'm please the blog has put temptation in your way to building your own cube and should you ever decide to create one then please do let us know about it.

The next blog should be along shortly which focuses on the 8x8 panel testing.

What a great and detailed write-up! I'm very impressed by your attention to details (and being a perfectionist when it comes to things like this, that's not a compliment I hand out all willy nilly)! I appreciate not only the details about the construction but also the reasoning behind why you made the desicions you did not to mention the time you took to make the diagrams. I've contimplated making an LED cube myself but haven't yet attempted it. This is in large part due to my aforementioned perfectionism and the daunting time investment I imagine it would take to get it just right. But I'm happy to see that I now have a wonderfully detailed resource to refer too, which makes the whole project that much more tempting!